Heretofore, in the art of stone cutting by means of a power-operated wire saw, no method for automatically controlling the main saw motor load has been known. The only available means of control have been mechanical feeds of various types which do not regulate the motor load. These prior art control devices do not adjust the sawing for constant horsepower, and therefore yield less cutting and rougher cutting.
The objective of this invention is to satisfy the need of the prior art to maintain the load on the main wire saw constant. If this load is constant, the resulting sawing is improved both in quantity and quality.
The invention utilizes a commercially available meter controller having internal switching contacts which are adjustable to close or open at a setting determined by the position of a meter control knob. The meter is set to a certain motor current value, usually ninety percent of the main motor's maximum current. The meter will then hold this value by down feeding the wire dolly whenever the motor current falls below the set value due to relaxing of the bowed cutting section of the wire. When the dolly down feed returns the proper bow curvature and cutting pressure to the wire, the load on the main drive motor and the motor current being drawn will return to the original preset value and the meter through its relay contacts will turn off the drive of the dolly.
The invention can be utilized on a wide range of saw types such as single wire strand saws or multiple wire saws. The meter controller is easily installed by disconnecting one power lead to the main saw drive motor and slipping a current transformer coil over the lead and reconnecting it. The meter controller turns on the wire dolly down feed motor whenever the power used by the wire driving motor decreases to a value below the preset optimum. The automatic power controller is simplified, economical, easy to adjust and yields increased sawing with improved quality.